As the size of hollow golf club heads has increased, weight distribution has become a major design consideration. In particular, in the quest to design in discretionary mass, it has become desirable to decrease the wall thicknesses of the portions that do not contribute directly to improved mass properties. Because of the thin wall and the large volumes of the golf club head, large portions of the heads act as membranes and vibrate relative to each other. In some instances, the vibration takes place at a relatively low frequency that results in unappealing sound during impact between the golf club head and a golf ball.
Sound tuning features have been incorporated into hollow bodied golf clubs. One example is described in U.S. Pat. No. 6,852,038 to Yabu for a Golf Club Head and Method of Making the Same. In that example, a hollow body golf club head includes rib-like walls that form the inner surface of the sole and crown. The sound emitted into the hollow cavity due to contact with a golf ball is directed rearward and parted laterally by the ribs. Sound bars are included in some embodiments that are located a small distance behind the club face and extends between the crown and sole. The sound bars are included to further part the sound vibrations.
Another example is described in U.S. Pat. No. 5,718,641 to Lin for a Golf Club Head that Makes a Sound when Striking the Ball. In that example, the golf club head includes a sound plate that is suspended in the hollow body of the club head that makes a sound and echoes the sound during impact between the club head and a golf ball. One edge of the sound plate is fixed to a wall of the hollow club head and the remaining edges are unattached so that the sound plate is able to vibrate relative to the remainder of the club head.
Others have added features to golf club heads to improve rigidity of the club head by reducing relative vibration between opposing walls to reduce the energy that is wasted in deforming the club head and to redirect that energy into the golf ball. For example, U.S. Pat. No. 6,524,197 to Boone for a Golf Club Head Having a Device for Resisting Expansion Between Opposing Walls During Ball Impact describes a feature designed for that purpose. The golf club head includes a tensioning device that extends between the crown and the sole. In particular, the tensioning device includes an elongate cylindrical member that extends through apertures in each of the crown and sole and enlarged ends that are unable to pass through the apertures. One of the enlarged heads is threaded so that a threaded end member may be used to tension the elongate cylindrical member thereby placing the hollow body in compression and increasing the rigidity of the hollow body.
It is desirable to provide a golf club that has sound tuning features for altering the sound produced by the golf club head during ball impact.